Optoelectronic ball grid array package with fiber

ABSTRACT

A photonic integrated circuit may be coupled to an optical fiber and packaged. The optical fiber may be supported by a fiber holder during a solder reflow process performed to mount the packaged photonic integrated circuit to a circuit board or other substrate. The optical fiber may be decoupled from the fiber holder, and the fiber holder removed, after completion of the solder reflow process.

RELATED APPLICATIONS

This Application is a divisional application of U.S. patent applicationSer. No. 14/927,016 filed on Oct. 29, 2015, which claims priority to andthe benefit under 35 U.S.C. § 119(e) to U.S. Provisional PatentApplication Ser. No. 62/069,877, filed Oct. 29, 2014 and entitled“OPTOELECTRONIC BALL GRID ARRAY PACKAGE WITH COILED FIBER,” the entiredisclosures of each of which are incorporated by reference herein intheir entirety.

BACKGROUND Field

The present application relates to packaging electronic componentshaving one or more optical fiber connections.

Related Art

Photonic integrated circuits (PICs) include optical componentsfabricated on a silicon substrate. Often an optical fiber is coupled tothe PIC to deliver optic signals to and from the PIC. The optical fibercan be edge-coupled to the PIC, or coupled to a surface of the PIC.

BRIEF SUMMARY

According to an aspect of the application, an apparatus is provided,comprising a substrate having a first surface, a photonic integratedcircuit (PIC) coupled to the substrate and having a first surfaceproximate the first surface of the substrate and a second surfaceopposite the first surface of the PIC and distal the first surface ofthe substrate, a lid, contacting the first surface of the substrate, anda fiber holder disposed on the lid. The apparatus further comprises anoptical fiber coupled to the PIC and in contact with the fiber holder.

According to an aspect of the application, a method is provided,comprising packaging a photonic integrated circuit (PIC) in a packagecomprising a substrate and a lid, mounting a fiber holder on the lid ofthe package such that the lid is between the PIC and the fiber holder,coupling an optical fiber to the PIC and mechanically coupling theoptical fiber to the fiber holder.

According to an aspect of the application, an apparatus is provided,comprising a substrate having a first surface, a photonic integratedcircuit (PIC) coupled to the substrate and having a first surfaceproximate the first surface of the substrate and a second surfaceopposite the first surface of the PIC and distal the first surface ofthe substrate and a lid, contacting the first surface of the substrateand at least partially covering the PIC, exhibiting at least oneretaining feature. The apparatus further comprises an optical fibercoupled to the PIC and in contact with the retaining feature of the lid.

BRIEF DESCRIPTION OF DRAWINGS

Various aspects and embodiments of the application will be describedwith reference to the following figures. It should be appreciated thatthe figures are not necessarily drawn to scale. Items appearing inmultiple figures are indicated by the same reference number in all thefigures in which they appear.

FIG. 1 illustrates a printed circuit board (PCB) on which a number ofphotonic integrated circuits (PICs) and a number of electronicintegrated circuits (EICs) are surface mounted, according to anon-limiting embodiment of the present application.

FIG. 2A is a side view of a package comprising a PIC, a fiber holder anda fiber coupled to the fiber holder, according to a non-limitingembodiment of the present application.

FIG. 2B is a top view of the package of FIG. 2A, according to anon-limiting embodiment of the present application.

FIG. 2C is a perspective view of the fiber holder shown in FIG. 2A,according to a non-limiting embodiment of the present application.

FIG. 2D is a view of the apparatus of FIG. 2A taken along line D-D.

FIG. 3 illustrates an alternative to the package illustrated in FIG. 2Ain which the packaged PIC is disposed on an interposer, according to anon-limiting embodiment of the present application.

FIG. 4A is a side view of an alternative to the package illustrated inFIG. 2A in which a fiber is coiled around a plane of the fiber holderthat is not parallel to the top surface of the PIC, according to anon-limiting embodiment of the present application.

FIG. 4B is a front view of the package of FIG. 4A, according to anon-limiting embodiment of the present application.

FIG. 5 is a side view of a packaged PIC in which the package isconfigured as a fiber holder to support an optical fiber, according to anon-limiting embodiment of the present application.

FIG. 6 illustrates the steps of a method to surface mount a packaged PICon a PCB, according to a non-limiting embodiment of the presentapplication.

DETAILED DESCRIPTION OF INVENTION

Applicant has appreciated that conventional techniques for packagingPICs are not practical when it is desired to co-package a PIC andelectrical circuitry operating in connection with the PIC, such asdrivers and/or application specific integrated circuits (ASICs). Thismay be particularly true when it is desired to have an optical fibercoupled to the PIC in a permanent manner, as opposed to with a pluggableconnection. ASICs and drivers may be packaged in ball grid array (BGA)packages, and such packages can be surface mounted on printed circuitboards (PCBs). Yet, doing so typically involves performing solderreflow, by placing the PCB and any components to be mounted thereon inan oven. The components are exposed to temperatures sufficiently high toachieve the desired solder reflow. Moreover, it may be desirable tomount many components on a PCB, providing only small gaps betweencomponents. Any optical fibers associated with a PIC may make closespacing of components on a PCB difficult. The fibers may catch on othercomponents being placed on the PCB, and may be broken off during theplacement of the packaged PIC or when passing through the oven.Moreover, the component is usually picked from a waffle pack and placedonto the PCB by a high-speed machine. Having fibers dangling from thecomponent would make this impractical. Moreover, the temperaturesexperienced in the oven during the solder reflow process may damage theoptical fibers, for instance by damaging any coating on the fibers.Thus, co-packaging a PIC with electronic circuitry in a packagecompatible with solder reflow processes may be difficult.

Therefore, aspects of the application provide apparatus and methods forretaining, during a reflow soldering process, an optical fiber coupledto a packaged PIC. By suitably retaining the optical fiber, the PIC maybe packaged in a type of package capable of being mounted on a PCB andsubjected to solder reflow, such that the PIC may in some embodiments beco-packaged with an ASIC, drivers, or other electronic circuitry. Onesuch type of package is a BGA package. The optical fiber may be retainedin a manner allowing the package containing the PIC to be placed inclose proximity to other components on a PCB, and may also prevent theoptical fiber from being subjected to temperatures sufficiently high todamage the fiber.

According to an aspect of the application a PIC is mounted in a packagecomprising a substrate and a lid. A fiber holder may be disposed on thepackage, for example on the lid. An optical fiber may be mechanicallycoupled to the fiber holder, for example by being wound or coiled aroundthe fiber holder. The fiber holder may be attached to the lid duringpackaging of the PIC, to retain the optical fiber, and may be removedafter completion of a solder reflow process involved in mounting thepackaged PIC to a PCB or other substrate. Thus, in some embodiments, thefiber holder may be temporary. The PIC may be co-packaged with an ASICand/or driver circuitry in some embodiments.

According to an aspect of the application a method for surface mountinga PIC on a PCB is provided. The method may comprise attaching a fiberholder to a packaged PIC, attaching to the fiber holder an optical fiberthat is coupled to the PIC, exposing the package to a solder reflowprocess to mount the packaged PIC on a PCB, removing the optical fiberfrom the fiber holder, and removing the fiber holder from the packagedPIC. The optical fiber, temporarily attached to the fiber holder, may beretained in a manner so as to prevent it from catching on othercomponents mounted on the PCB. The optical fiber may be permanentlycoupled to the PIC in some embodiments.

According to an aspect of the application, a PIC coupled to an opticalfiber is in a package including a substrate and a lid. The lid includesa fiber retaining feature. The optical fiber coupled to the PIC isengaged with the fiber retaining feature of the lid, at least during asolder reflow process performed on the packaged PIC. In someembodiments, the fiber retaining feature is a groove and the opticalfiber may be coiled around the groove. In some embodiments, the packageis a BGA package, and the package may include an ASIC or a drivercircuit in addition to the PIC.

Various aspects will be described herein as including a “fiber holder.”Alternative terminology may be used herein, including “fiber block,”“fiber retainer,” and “fiber support,” as non-limiting examples.

Various aspects will be described herein as including a “strength.”Alternative terminology may be used herein, including “amplitude,”“power,” and “magnitude,” as non-limiting examples.

The aspects and embodiments described above, as well as additionalaspects and embodiments, are described further below. These aspectsand/or embodiments may be used individually, all together, or in anycombination of two or more, as the application is not limited in thisrespect.

As described, aspects of the present application relate to a packagedPIC which is coupled to an optical fiber and which may be mounted on achip carrier, such as a PCB, together with other components. FIG. 1illustrates an apparatus 100 including a printed circuit board (PCB) 101according to an aspect of the present application. PCB 101 may compriseone or more PICs, electronic integrated circuits (EICs), and/or laserchips. For example, as illustrated, a PIC 102, EIC 104, and laser chip106 may be mounted on the PCB 101. The PIC 102 is coupled to one or moreoptical fibers to route optical signals into or out of the PIC. In thenon-limiting example illustrated, the PIC 102 is coupled to threeoptical fibers 1161, 1162, and 1163, although at least some aspects ofthe present application apply to a packaged PIC with one or more coupledoptical fibers. The components mounted on the PCB 101 may optionally beelectrically interconnected via electrical traces 108 of any suitablekind, such as copper traces.

The PIC 102 may comprise photonic circuitry to generate, modulate,detect or process light in any suitable fashion. For example, the PIC102 may be a transceiver for optical communications. The various aspectsdescribed herein are not limited to the particular type of PIC included.FIG. 1 shows the optical fibers 1161, 1162, and 1163 as being edgecoupled to the PIC 102. However, in some embodiments, the opticalfiber(s) may be vertically coupled to the packaged PIC, for examplethrough optical gratings.

The EIC 104 may comprise electronic circuitry to process digital and/oranalog signals. In some embodiments the EIC 104 may comprise modulatordrivers, trans-impedance amplifiers or clock recovery circuits. In someembodiments, the EIC 104 may be an application-specific integratedcircuit (ASIC), a field programmable gate array (FPGA), system on a chip(SoC) or a microcontroller, and may include any combination of logicunits, volatile and non-volatile memory units, RF transceivers,analog-to-digital converters and digital-to-analog converters.

In some embodiments, EIC 104 may disposed next to and in electriccommunication with packaged PIC 102, as illustrated. However, as will bedescribed further below, for example in connection with FIGS. 2A-2D,aspects of the present application allow for co-packaging of PICs withEICs. That is, embodiments of the present application allow for PIC 102and EIC 104 to be co-packaged, for example in a BGA package, eitherdirectly on a BGA substrate or on an interposer on the BGA substrate.Such co-packaging may be facilitated by aspects of the presentapplication providing a manner for supporting the optical fibers 1161,1162, and 1163 during a solder reflow process.

The optical fibers of the apparatus 100 may be coupled to componentsexternal to the PCB 101 or to components on the PCB 101, or to acombination of both. For example, optical fibers 1161 and 1162 may beconnected to optical components not mounted on PCB 101 (not shown).Optical fiber 1163 may be connected and optically coupled to laser chip106. Laser chip 106 may comprise distributed feedback lasers (DFBs),distributed Bragg reflector lasers (DBRs), rings lasers, vertical-cavitysurface-emitting lasers (VCSELs), quantum well lasers, quantum cascadedlasers, or any other suitable semiconductor laser. For example, if thePIC 102 represents an optical transceiver, the laser chip 106 mayprovide an input signal to the optical transceiver via the optical fiber1163. Laser chip 106 may further comprise a thermo-electric cooler tostabilize the operating temperature.

Components on a PCB are typically positioned near each other, toconserve space. For example, it may be desirable for the distances d1and d2 between adjacent components on PCB 101 to be less than 30 cm,less than 1 cm, less than 1 mm, less than 100 μm, between 100 μm and 2mm, or any value or range of values within such ranges. Consequently,assembling the components on the PCB can be technologically challenging,especially in the presence of optical fibers dangling around the board.For example, the optical fibers 1161 and 1162 and 1163 may make itdifficult to position EIC 104 in close proximity to the PIC 102. It isalso difficult for a high-speed pick-and-place machine to handlecomponents with dangling fibers.

According to an aspect of the present application, a fiber holder isprovided with the packaged PIC 102 to support the optical fibers, atleast during mounting processes such as solder reflow and placement ofthe PIC 102 or other components on the PCB 101. A non-limiting exampleof a packaged PIC including a fiber holder is described in connectionwith FIG. 2A.

FIG. 2A illustrates a cross-sectional view of an apparatus 200representing a co-packaged PIC and EIC with a fiber holder to support anoptical fiber coupled to the PIC. Apparatus 200 may therefore serve asPIC 102 of FIG. 1 in a non-limiting embodiment.

The apparatus 200 includes PIC 202 and EIC 203 coupled to a substrate201 and mounted on the PCB 101. The PIC 202 may be in electriccommunication with the EIC 203 through electrical connections 204, suchas vias, metal pillars, solder bumps, conductive traces patterned in thesubstrate 201, or any other suitable electrical connections. A lid 210covers the PIC 202 and EIC 203, and may dissipate heat generated by thetwo chips. The package may further comprise a fiber assembly 212connected to an optical fiber 216, which may be a single mode opticalfiber (SMF) or any other type of optical fiber. While FIG. 2A shows oneoptical fiber 216 connected to fiber assembly 212, fiber assembly 212may alternatively be connected to a plurality of optical fibers. Thepackage may further include, at least temporarily, a fiber holder 230configured to retain optical fiber 216. The package may be surfacemounted on PCB 101 via a ball grid array (BGA) 205 of solder balls, orvia other suitable electrical connection.

In some non-limiting embodiments, fiber assembly 212 is mounted in thepackage so as to enable optical access to the PIC through optical fiber216. The coupling of optical fiber 216 to the PIC 202 may be permanent,rather than pluggable. Thus, in at least some embodiments, it may not bepossible to remove the optical fiber 216 from the PIC 202 for the solderreflow process. Optical fiber 216 may be arranged in fiber assembly 212in any suitable manner. For example, fiber assembly 212 may compriseV-shaped or U-shaped grooves. Optical fiber 216 may be disposed in anyof such grooves. While coupling optical fibers to optical waveguides hasvery low tolerance to misalignments (typically +/−0.5 um), the use ofgrooves allows for high-precision positioning of the fiber with respectto the PIC, thus minimizing insertion loss. While FIG. 2A shows PIC 202as being coupled to one optical fiber, more than one optical fiber maybe coupled to PIC 202.

The fiber holder 230 may be used to support the optical fiber 216 duringcertain steps of manufacturing, such as during placement of the packagedPIC 202 and EIC 203 on the PCB 101 and/or solder reflow for affixing thesubstrate 201 to the PCB 101. Fiber holder 230 may be disposed on top ofthe package. For example, it may be attached to lid 210 and secured viaone or more screws, threaded rods, or other fastening mechanism suitableto withstand the temperatures of solder reflow. Alternatively, fiberholder 230 may be secured to the lid 210 via a snap-fit or press-fit ormagnetic connection.

The fiber holder 230 may perform multiple functions. Firstly, itprevents loose portions of optical fiber 216 from dangling around PCB101 during the surface-mounting phase. Dangling fibers may accidentlysnap or snag on other components of the PCB 101 and may consequentlycause impairments to the operation of the PIC 202, the apparatus 200,and the PCB 101 more generally. Accordingly, the fiber holder 230 mayinclude one or more fiber retaining features. Non-limiting examples ofsuch fiber retaining features include a groove, channel, fiber path,opening, or combination of those features. In the illustrated example,the fiber holder 230 includes a groove 207 representing a narrowercentral region of the fiber holder. By winding or coiling optical fiber216 around fiber holder 230, as shown, the potential negativeconsequences of having optical fiber 216 dangle loosely are avoided.

FIG. 2C shows a perspective view of the fiber holder 230. As shown, thefiber holder 230 comprises a bottom plate 232, a top plate 234 and apillar 236. The fiber holder 230 may be a spool. The pillar 236 maydefine a narrower region than the bottom plate 232 and top plate 234,and may serve as a feature around which optical fiber 216 may be wound,as illustrated. The optical fiber may be wound by hand or in anautomated manner using suitable machinery. While in the figure pillar236 exhibits a rectangular cross-section, any suitable cross-sectionalshape may be used. Optical fiber 216 may be coiled around pillar 236through an opening 213 provided in bottom plate 232. The opening 213 mayallow for the optical fiber 216 to be wound around the fiber holder 230without requiring the optical fiber 216 to extend as far from itsconnection to the PIC 202 at the fiber assembly 212.

When the optical fiber 216 is wound or coiled about the fiber holder230, it may be done with a radius smaller than the minimum bend radiusthat causes optical losses. This is because the optical fiber 216 isbeing coupled to the fiber holder 230 for purposes of mounting thepackaged PIC on the PCB 101 through a solder reflow process, duringwhich the optical fiber 216 will not be in use. Subsequent to completingthe mounting process, the optical fiber 216 may be removed from thefiber holder 230 and allowed to assume a configuration which does notimpart to the optical fiber 216 a bend radius smaller than that whichcauses optical losses. In some embodiments, optical fiber 216 is coiledaround fiber holder 230 with a bend radius between approximately 1 mmand 1 cm, between approximately 3 mm and 10 cm, between approximately 5mm and 5 cm, or any other value or range of values within such ranges.The pillar 236 may have cross-sectional dimensions giving rise to thebend radius of the coiled optical fiber 216 within any of the rangeslisted, as non-limiting examples.

In the non-limiting embodiment shown in FIGS. 2A and 2C, the opticalfiber may be coiled around an axis that is substantially perpendicularto the top surface of PIC 202, meaning that the optical fiber may becoiled within a plane substantially parallel to a plane of the PIC 202.However, as will be described further below in connection with FIGS.4A-4B, other suitable configurations exhibiting coiling axes notperpendicular the top surface of the PIC are also possible.

Moreover, although FIGS. 2A and 2C illustrate the optical fiber 216being wound around the fiber holder 230, not all embodiments are limitedin this respect. For example, the optical fiber 216 may be positioned ina zig-zag pattern, back-and-forth pattern, or other suitableconfiguration with respect to a fiber holder. Thus, coiling or windingthe optical fiber around a fiber holder represents a non-limitingexample of a manner of coupling the two.

Referring still to FIG. 2C, the fiber holder 230 may include a hole 215configured to receive or accommodate a coupler to couple the fiberholder 230 to the lid 210. For example, hole 215 may accommodate ascrew. Other features may additionally or alternatively be provided toallow for temporarily coupling the fiber holder 230 to the lid 210.

Referring again to FIG. 2A, while one end of optical fiber 216 iscoupled to PIC 202 at the fiber assembly 212, the other end may besecured to fiber holder 230 through a fiber clip 270 or any othersuitable securing mechanism, thus keeping fiber 216 from moving after itis coupled to the fiber holder 230. Fiber clip 270 may alternatively beplaced on any other suitable component of apparatus 200. As will bedescribed further below in connection with FIG. 6 , the end of theoptical fiber not coupled to the PIC 202 may eventually be coupled toanother component on the PCB or to a component external to the PCB.Thus, it should be appreciated that in at least some embodiments thefiber holder 230 retains or supports a portion of the optical fiber notincluding the ends of the optical fiber. For example, a central ormiddle portion of the length of the optical fiber may be retained by thefiber holder 230.

A second function performed by the fiber holder 230 may be to keepoptical fiber 216 at a low temperature during the reflow soldering.Typical soldering reflow may reach temperatures of 260° C. or higher,which may damage the optical fiber's protective jacket. In someembodiments, fiber holder 230 is made of a material exhibiting highthermal mass and high thermal conductivity so as to slowly respond toincreases in temperature while absorbing heat from optical fiber 216. Insome embodiments, fiber holder 230 is made of copper or aluminum. Fiberholder 230 may also have a shiny surface to further reflect heat. Tofurther facilitate temperature control of the optical fiber 216 as wellas the fiber assembly 212, a thermal pad 214 may be disposed between andin contact with fiber assembly 212 and fiber holder 230. Thermal pad 214may keep fiber assembly cool during reflow soldering. The thermal pad214 may be of any suitable material, such as paraffin wax or silicone.

A third function performed by the fiber holder 230 is that it maylaterally extend beyond the edge of the lid 210 in the x-direction ofFIG. 2A, acting as a cover or overhang for the fiber assembly 212 asshown in FIG. 2A. By covering fiber assembly 212, fiber holder 230 mayprovide mechanical protection against potential collisions with othercomponents that may occur throughout the surface mounting process. Theamount of overhang H may be between 0.5 mm and lmm, or any othersuitable amount.

PIC 202 may be fabricated on a silicon-on-insulator (SOI) wafer, a bulksilicon wafer, an indium phosphide wafer or any other suitablesemiconductor wafer. In some embodiments, substrate 201 is made ofceramic. In other embodiments substrate 201 is made of an organicmaterial. In some embodiments, lid 210 is used as a heat sink todissipate heat generated by the PIC 202 and EIC 203. The lid 210 may beformed of a material exhibiting a high thermal conductivity, such asaluminum or copper. A thermal pad or thermal paste 218 may be disposedbetween PIC 202 and lid 210, and between EIC 203 and lid 210 to ensureefficient heat transfer to the lid. The lid 210 may further comprisefins to transfer heat out of the package (not shown).

FIG. 2B shows a top view of the package including substrate 201, PIC202, EIC 203, fiber assembly 212, optical fiber 216 and lid 210. In someembodiments lid 210 may comprise a top surface (shown as shaded) and anouter wall 211 (shown as solid). The lid's outer wall 211 may be placedin contact with substrate 201. While, the lid's outer wall 211 maysurround the two chips, an opening may be provided to enable access toPIC 202 through fiber assembly 212 as shown in FIG. 2B. This can also beseen by reference to FIG. 2D, which is taken along line D-D of FIG. 2A.As shown, the lid 210 contacts the substrate 201, but access is providedto PIC 202.

To efficiently couple optical signals between optical fiber 216 and PIC202, fiber assembly 212 may be positioned as close to PIC 202 aspossible. Accordingly, as shown in FIG. 2A, a portion of an edge of lid210 and a portion of an edge of substrate 201 may be partially etched soas to accommodate fiber assembly 212.

In some non-limiting embodiments, PIC 202 may be flip-chip mounted onsubstrate 201. Accordingly, the handle of the PIC 202 faces lid 210 andthe planar photonic circuitry faces substrate 201. However, PIC 202 mayalternatively be mounted on substrate 202 without being flipped. In sucha configuration, one or more optical fibers may be optically coupled tothe top surface of the PIC through optical gratings. The optical fibersmay be further coupled to fiber holder 230.

In some embodiments, an interposer may be used to route electricalsignals between PIC 202 and EIC 203. Interposers may be used to maximizethe connection density of the electric path between PIC 202 and EIC 203.FIG. 3 illustrates an alternative embodiment comprising an interposer317. In the non-limiting example shown in FIG. 3 , interposer 317 isdisposed on substrate 201, making electrical contact with it throughmetal pillars or solder bumps. Electric connection between interposer317 and PIC 202 may be achieved with through silicon vias (TSV). TSVsmay exhibit electric capacitances order of magnitudes lower than thoseassociated with metal pillars or solder bumps. For instance thecapacitance associated to the TSVs shown in FIG. 3 may be less than 1pF, less than 100 fF, or less than 1 fF, as non-limiting examples.Similarly, electric connection between interposer 317 and EIC 203 may beachieved with TSVs. However, any other suitable form of electricconnection may be used. Due to the low electric capacitance, theresulting bandwidth of the electric path connecting PIC 202 to EIC 203is substantially higher than that of a path where an interposer is notused. In some embodiments, such bandwidth may be greater than 1 GHz,greater than 10 GHZ, greater than 40 GHz, between and 30 GHz, or anyvalue or range of values within such ranges.

The other components in FIG. 3 have already been described and remainthe same as previously described.

FIG. 4A and FIG. 4B illustrate a side view and a front view,respectively, of an alternative embodiment in which an optical fiber 416is coiled around an axis of a fiber holder that is substantiallyparallel the top surface of PIC 202, such that the optical fiber iscoiled in a plane that is not parallel the top surface of PIC 202. Asshown in FIG. 4B, fiber holder 430 may comprise pillars 432 and 434,each pillar resting on lid 210 and connected to each other through beam436. Optical fiber 416 may be connected to fiber assembly 212 at one ofits two ends and may further be coiled around beam 436. The second endof optical fiber 416 may be secured to fiber holder 430 (not shown inthis figure) though any suitable securing mechanism, such as a clip ofthe type previously described in connection with FIG. 2A. Fiber holder430 may be attached to lid 210 in any of the manners previouslydescribed in connection with fiber holder 230.

FIG. 5 illustrates an apparatus 500 according to an alternativeembodiment, in which the lid of the package may serve as the fiberholder. In the non-limiting example, lid 510 may be configured to retainoptical fiber 516. Namely, the lid 510 may have a shape substantiallylike that of fiber holder 230 of FIG. 2A, previously described. In thenon-limiting embodiment shown in FIG. 5 , optical fiber 516 is coiledaround an axis that is substantially perpendicular to the top surface ofPIC 202. However, other configurations in which optical fiber 516 iscoiled around an axis not perpendicular to the top surface of PIC 202may be used. For example, a configuration similar to that shown in FIG.4B may be employed.

In some embodiments, lid 510 may be temporarily mounted on the packageto facilitate surface mounting operations on PCB 101. For example, thelid 510 may be added prior to performing a solder reflow processinvolving the apparatus 500, and removed after completion of the solderreflow process. In other embodiments, lid 510 may be permanently mountedon the package. In such situations, the optical fiber 516 may be coiledaround the lid 510 during surface mounting procedures, including solderreflow, but may be removed from the lid 510 thereafter. Lid 510 may bemade of a material exhibiting high thermal mass and high thermalconductivity so as to slowly respond to increases in temperature whileabsorbing heat from optical fiber 516. In some embodiments, lid 510 ismade of copper. Lid 510 may also be coated with silver to furtherreflect heat.

FIG. 6 illustrates the steps of a method for surface mounting a packagedPIC on a PCB, according to an aspect of the present application. Method600 may be used in connection with the apparatus 200 of FIG. 2A, as anexample, and therefore reference to the apparatus 200 is made indescribing the method. However, the described method may also apply tothe apparatus of FIGS. 4A-4B. Moreover, alternative methods of mountingthe packaged PIC may be used.

Method 600 begins at step 602, where PIC 202 is fabricated. PIC 202 maybe fabricated in a semiconductor foundry or in any suitable fabricationfacility, as the various aspects of the present application are notlimited in this respect. PIC 202 may be fabricated on SOI wafers. PIC202 may comprise one or more optical transceivers for opticalcommunications, including coherent transceivers. PIC 202 may furthercomprise edge couplers such as spot-size converters and polarizationdevices such as polarization splitters and rotators.

In step 604, PIC 202 may be packaged. For example, the PIC may bepackaged with substrate 201 and lid 210, and fiber assembly 212 may beconnected to the PIC, as shown in FIG. 2A. As previously described, insome embodiments a PIC is co-packaged with an electronic circuit. Thus,for example, step 604 may include packaging the PIC with an electroniccircuit, such as EIC 203.

In step 606, fiber holder 230 may be mounted on the package. Fiberholder 230 may be mounted in any of the manners previously describedherein. For example, it may be screwed, snap-fitted or press-fitted onthe package as described previously.

In step 608, optical fiber 216 may be coupled to or placed in contactwith the fiber holder. For instance, optical fiber 216 may be coiledaround fiber holder 230 as shown in FIG. 2C. As previously described,the optical fiber may be attached to the fiber holder by hand, or in anautomated fashion, for example using suitable machinery.

In step 610, the packaged PIC may be disposed on a PCB, such as PCB 101.PCB 101 may further comprise a plurality of EICs, such as ASICs, FPGAs,SoCs, and/or driver circuits. In step 610, the end of optical fiber 216that is not attached to fiber assembly 212 may be secured to fiberholder 230 with a clip as shown in FIG. 2A.

In step 612, PCB 101 may be exposed to a reflow soldering process tomelt and permanently connect the contacts between PCB 101 and substrate201. Throughout the reflow soldering, optical fiber 216 may be securedto fiber holder 230 so as to not be in the way of other componentsmounted on the PCB. In addition, by maintaining thermal contact withfiber holder 230, optical fiber 216 may be kept to a temperature lowenough to prevent damage to the fiber jacket, if any. In someembodiments, the reflow may reach a temperature of 260° C. for severalseconds or more, such as between 10 seconds and 30 seconds, between 10seconds and one minute, or any other duration suitable to adhere thepackaged PIC to the PCB.

In step 614, the optical fiber may be uncoupled from fiber holder. Forexample, in the non-limiting embodiment of FIG. 2A, optical fiber 216may be uncoiled from fiber holder 230. In step 616, fiber holder 230 maybe removed from the package.

In step 618, optical fiber 216 may be spliced to an optical componentdisposed on or outside PCB 101.

Again, it should be appreciated that alternatives to the method 600 maybe implemented. For example, in those embodiments in which a packagelid, such as lid 510 of FIG. 5 serves as the fiber holder, the lid maynot be removed after the solder reflow process. Further alternatives arepossible.

The aspects of the present application may provide one or more benefits,some of which have been previously described. Now described are somenon-limiting examples of such benefits. It should be appreciated thatnot all aspects and embodiments necessarily provide all of the benefitsnow described. Further, it should be appreciated that aspects of thepresent application may provide additional benefits to those nowdescribed.

Aspects of the present application provide simplicity in surfacemounting a packaged PIC on a PCB when it is desired to have an opticalfiber coupled to the PIC in a permanent manner, as opposed to with apluggable connection. Throughout the surface mounting process thefiber(s) may catch on other components being placed on the PCB, and maybe broken off during the placement of the packaged PIC or when passingthrough the reflow oven. Retaining the fiber with a fiber holder mountedon the package allows the package containing the PIC to be placed inclose proximity to other components on a PCB while avoiding anyimpairment of the fiber. Moreover, the thermal properties of the fiberholder may be selected to prevent the fiber from being subjected totemperatures sufficiently high to cause damage to the fiber.

Aspects of the present application allow for the packaged PIC with apermanent optical fiber connection to be treated much like aconventional packaged EIC for purposes of a surface mounting process. Inthis manner, the packaged PIC may be placed on a PCB and subjected toPCB processing in the same manner as done for EICs.

Aspects of the present application facilitate co-packaging of PICs anddrivers and/or ASICs. The aspects described herein allow for PICs havingpermanent optical fiber connections to be packaged in BGA packages orother packages compatible with packaging EICs. Thus, a PIC and EIC maybe packaged together.

Having thus described several aspects and embodiments of the technologyof this application, it is to be appreciated that various alterations,modifications, and improvements will readily occur to those of ordinaryskill in the art. Such alterations, modifications, and improvements areintended to be within the spirit and scope of the technology describedin the application. It is, therefore, to be understood that theforegoing embodiments are presented by way of example only and that,within the scope of the appended claims and equivalents thereto,inventive embodiments may be practiced otherwise than as specificallydescribed. In addition, any combination of two or more features,systems, articles, materials, and/or methods described herein, if suchfeatures, systems, articles, materials, and/or methods are not mutuallyinconsistent, is included within the scope of the present disclosure.

Also, as described, some aspects may be embodied as one or more methods.The acts performed as part of the method may be ordered in any suitableway. Accordingly, embodiments may be constructed in which acts areperformed in an order different than illustrated, which may includeperforming some acts simultaneously, even though shown as sequentialacts in illustrative embodiments.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified.

The terms “approximately” and “about” may be used to mean within ±20% ofa target value in some embodiments, within ±10% of a target value insome embodiments, within ±5% of a target value in some embodiments, andyet within ±2% of a target value in some embodiments. The terms“approximately” and “about” may include the target value.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. The transitional phrases “consisting of” and “consisting essentiallyof” shall be closed or semi-closed transitional phrases, respectively.

What is claimed is:
 1. A method, comprising: packaging a photonicintegrated circuit (PIC) in a package comprising a substrate and a lid,the substrate having a first surface and a second surface opposite thefirst surface of the substrate, the PIC having a first surface; mountinga fiber holder on the lid of the package such that the lid is betweenthe PIC and the fiber holder, wherein the first surface of the substrateis proximate the first surface of the PIC and the second surface of thesubstrate is distal the first surface of the PIC; coupling an opticalfiber to the PIC, the lid contacting the first surface of the substrateand at least partially covering the PIC; and mechanically coupling theoptical fiber to the fiber holder.
 2. The method according to claim 1,further comprising surface-mounting the package on a chip carrier. 3.The method according to claim 2, further comprising securing an end ofthe optical fiber on the fiber holder.
 4. The method according to claim1, further comprising performing reflow soldering of the package.
 5. Themethod according to claim 4, further comprising removing the fiberholder from the package subsequent to the reflow soldering.
 6. Themethod according to claim 1, wherein mechanically coupling the opticalfiber to the fiber holder comprises coiling a portion of the opticalfiber around the fiber holder.
 7. The method according to claim 6,wherein the portion of the optical fiber is coiled around the fiberholder with a radius that is less than a minimum bend radius of theoptical fiber.
 8. The method according to claim 1, further comprisingsplicing the optical fiber to an optical component.
 9. The methodaccording to claim 1, wherein mounting the fiber holder on the lid ofthe package comprises mounting the fiber holder with at least one screwinserted on the lid.
 10. The method according to claim 1, whereinmechanically coupling the optical fiber to the fiber holder comprisescoiling a portion of the optical fiber around the fiber holder.
 11. Themethod according to claim 1, wherein the lid exhibits at least oneretaining feature.
 12. The method according to claim 11 furthercomprising contacting the at least one retaining feature of the lid withthe optical fiber.